Class MutableHeaders

starlette/datastructures.py:577–661

class MutableHeaders(Headers):
    def __setitem__(self, key: str, value: str) -> None:
        """
        Set the header `key` to `value`, removing any duplicate entries.
        Retains insertion order.
        """
        set_key = key.lower().encode("latin-1")
        set_value = value.encode("latin-1")

        found_indexes: list[int] = []
        for idx, (item_key, item_value) in enumerate(self._list):
            if item_key == set_key:
                found_indexes.append(idx)

        for idx in reversed(found_indexes[1:]):
            del self._list[idx]

        if found_indexes:
            idx = found_indexes[0]
            self._list[idx] = (set_key, set_value)
        else:
            self._list.append((set_key, set_value))

    def __delitem__(self, key: str) -> None:
        """
        Remove the header `key`.
        """
        del_key = key.lower().encode("latin-1")

        pop_indexes: list[int] = []
        for idx, (item_key, item_value) in enumerate(self._list):
            if item_key == del_key:
                pop_indexes.append(idx)

        for idx in reversed(pop_indexes):
            del self._list[idx]

    def __ior__(self, other: Mapping[str, str]) -> MutableHeaders:
        if not isinstance(other, Mapping):
            raise TypeError(f"Expected a mapping but got {other.__class__.__name__}")
        self.update(other)
        return self

    def __or__(self, other: Mapping[str, str]) -> MutableHeaders:
        if not isinstance(other, Mapping):
            raise TypeError(f"Expected a mapping but got {other.__class__.__name__}")
        new = self.mutablecopy()
        new.update(other)
        return new

    @property
    def raw(self) -> list[tuple[bytes, bytes]]:
        return self._list

    def setdefault(self, key: str, value: str) -> str:
        """
        If the header `key` does not exist, then set it to `value`.
        Returns the header value.